Method of recovering valuable constituents of ores.



H. G. c. THOFEHRN.'

METHOD OF RECOVERING VALUABLE CONSTITUENTS 0F ORES.

APPLICATION FILED MAR. 3, I915.

1,210,724. Patented Jan. 2,1917.

WIJVES 5S OR 41 I I i /H I I WA/forney HERMANN G. C. THOFEHRN,

or PITTSBURGH, PENNSYLVANIA.

METHOD OF BECOVERING VALUABLE GONSTITUENTS F ORE-S.

Specification of Letters Patent.

Patented J an. 2, 1917.

Application filed March 3, 1915. Serial No. 11,884.

1 exact description of the invention, such as will enable others skilled in the art to which,

it appertains to make and use the same.

This invention relates to an improved method of recovering valuable constituents of ores,one object of the invention being to provide a simple, economical and commercia'lly feasible process for separating the metal from the mineral or gangue constituents of the ore, with the use of nitric acid evolved or formed in an aqueous mixture containing comminuted ore.

A further object is to utilize nitrogen oxid from electrically treated atmospheric air to form nitric acid in an aqueous mixture containing comminuted ore and to also utilize the pressure of air forced with the nitrogen oxid into said mixture, to agitate the latter and thus bring all particles of the ore within the active zone of the evolved nitric acid.

A further object is to provide electrical means which will augment the quantity of nitric acid formed in the aqueous mixture of comminuted ore.

With these and other objects in view, the invention consists in certain novel steps in the process of treating ore as hereinafter set forth and pointed out in the claims.

In the accompanying drawings, Figure 1 is a view illustrating one construction of apparatus which may be employed for carrying my improved method into effect, and Fig. 2 is a view showing an elongated construction' which may be used in'treating a large quantity of ore.

Most all metals contained in the minerals are soluble in nitric acid and in carrying out my improved method, I employ such acid to dissolve said metaland' thereby separate the same from the mineral or gangue constitu- 50 ents of the ore. It is not feasible-however,

to use nitric. acid of commerce because that would necessitate the employment of vessels made of a material which would resist the action of such nitric acid. Vessels of this 55 character are generally very expensive and delicate to handle. I overcome this difficulty by the use of nitrogen oxid, preferably nitrogen pentoxid, N 0 In bringing this gas in contact with water, nitric acid, according to the formula,

is obtained.

The nitrogen pentoxid may be produced by any suitable apparatus, of which there are many. This pentoxid coming from the source of supply is generally greatly diluted with air, giving a concentration of rarely more than three per cent. The presence of this air in carrying out my method is not only desirable but quite important, as will be hereinafter more particularly pointed out.

In carrying out my improved method, I make an aqueous mixture of comminuted ore, in a tank 1 having a conical bottom or a bottom made of inclined planes, made generally of plain wood. At the point of the angle formed by the inclined planes of the bottom, I introduce the nitrogen pentoxid resulting from electrical treatment of atmospheric air and accompanying air under pressure suflicient to overcome the column of aqueous mixture contained in the tank.

Nitrogen oxid or pentoxid may be produced from air, by means of an electrical apparatus 2, in which an alternating electric current is preferably used to bring about the oxidation of the nitrogen of the air which is caused to circulate through the apparatus. The construction and mode of operation of apparatus such as illustrated at 2 are well known in the art and need not be more particularly described herein. From the apparatus 2, the nitrogen oxid is taken by a pump 8 and from thence to a heater 4 (of any suitable construction), which in many cases may be useful for heating the gas in order to enhance or augment the reactions in the tank 1, to the bottom of which latter, the nitrogen oxid gas and air are conducted by the pipe 5.

If desired, the pump 3 might be located in advance of the apparatus 2, instead of between said apparatus' and the heater 4:, or if preferred, the pump could be located between the heater 4.- and the tank 1.

The nitrogen pentoxid gas, together with air under pressure entering through the bot tom of the tank will, in bubbling through the aqueous mixture of ore, cause such agitation of the same as to keep all solid material in suspension and cause it to circulate vertically in such a way that all the particles of the comminuted material will come in contact with nitric acid at the point where it is formed in the liquid. As the reaction between the pentoxid of nitrogen and the wa ter which contains the mineral in suspension is almost instantaneous, and as every particle of the material in the agitated aqueous mixture will pass progressively through the zone of the jet of air and nitrogen gas, all of the combined mineral and metal will be submitted to the action of nascent nitric acid at the moment the latter is formed. In operating in this manner, much diiiusion of nitric acid throughout the watery mixture is avoided, but the action of the nitric acid is confined while in formation to a relatively small area in effecting the reaction between the nitric acid and the metal particles of the ore. By binding the nitric acid with the dissolved content of the ore immediately upon the formation of the nitric acid, the diffusion of free acid throughout the aqueous mixture will be sufliciently restricted to permit the use of wooden vessels. r

In order to hasten the operation of the process, it will be found desirable to accelerate the reactions by which the nitric acid is caused to dissolve the metallic content of the orein the lower part of the tank. This I accomplish by causing the combined air and nitrogen pentoxid gas to come in contact with the water and comminuted ore, between two electrodes 6, 7, which are included in an electric circuit supplied by an electric current of a density appropriate for the Work to be done, said current being preferably supplied by a suitable generator illustrated diagrammatically at 8, and in the circuit of which, the electrodes are connected in series. The. electric current in passing through the aqueous mixture, in the immediate neighborhood of the entrance of the nitrogen pentoxid gas, decomposes the water in producing hydrogen and oxygen. These two gases in nascent state, and in contactwith the nitrogen pentoxid blown into the apparatus, accelerates the reactions very considerably.

It may be stated by way of illustration, that in treating one ton of material, an electric current of twenty amperes in the circuit of theelectrodes would be efiective for the purpose stated.

When large quantities of material are to be treated, the tank may be made rectangular as shown at 9, Fig. 2, instead of conical as shown in Fig. .1, and provided with'a bottom consisting of converging inclined members 10. A pipe, 11 having numerous perforations 12 is located in the bottompart of the tank, and connected with the source of supply of nitrogen, gas and air. The electrodes 13 may be made in the form of plates disposed in planes approximately parallel with the inclined members 10 forming the bottom of the tank. Any desired number of positive and negative electrodes may be employed,-all the positive plates being connected with one side of the circuit and all the negative plates being connected with the other side.

During the operation. of my improved method, all soluble substances, such as oxids, carbonates, sulfids, limes, etc., enter into solution and are mostly transformed into nitrates,'w hi-le the insoluble parts, mostly silica, remain as gangue.

When the operation of the method hereinbefore described has been completed, the

liquid, togetherwith the remaining gangue may be withdrawn from the tank, and caused to flow into a suitable settling tank, from which the clear liquid will be withdrawn for further treatment to recover. the. valuable.

contents. Having fully described my invention what I claim as new and desire-to secure by Letters-Patent, is r 1. The herein described method, consisting in discharging pentoxid of nitrogen gas into an aqueous mixture of comminutedore.

2. The herein described method consisting in setting up an electrical field between electrodes in an aqueous 'IIllXlJllIG of comminuted ore, and discharging nitrogen pentoxid gas into the aqueous mixture inthe causing all particles of said mixture to pass progressively through the zone of the reaction between said mixture. 6. The herein described method, consistmg in producing nitrogen pentoxid gas and gas and the water of the injecting said oxid of nitrogen with atmospheric air under pressure intoan aqueous mixture of comminuted ore, whereby nitric acid is formed in said mixture.

7. The herein described method consisting in mixing comminuted ore with water, injecting nitrogen pentoxid gas into said mixture and thereby generating nitric acid within said mixture and simultaneously causing said nitric acid to react on metallic form nitrates-of constituents of the ore and the same. i

8. The herein described method, consisting in mixing comminuted ore with Water, setting up an electrical field between electrodes in said mixture and forcing nitrogen pentoxid and air into the electrical field Within said mixture, whereby free nitric acid Will be formed Within said mixture and immediately react upon the metallic constituents of the ore.

9. The herein described method, consisting in mixing comminuted ore with Water,

Copies of this patent may be obtained for five cents each, by addressing the Washington, D. C.

generating nitrogen pentoxid gas from atmospheric air, heating said gas, and forcing the gas so generated With air into saidmixture of comminuted ore and Water.

In testimony whereof, I have signed this specification in the presence of tWo subscribing Witnesses.

HERMANN G. C. THOFEHRN.

Witnesses:

W. W. DAILEY, F. H. ALLISON.

Commissioner of Patents, 

